Pathophysiology of CV Disease Flashcards
Define heart failure
a complex syndrome initiated by an inability of the heart to maintain normal CO at normal filling pressure - as a consequence of heart disease
- BUT not all heart disease will go on to heart failure
Which species is most commonly affected by heart disease?
Dogs, cats less comon
What are the 3 types of heart failure?
- Forward failure
- inadequate output at normal pressures (eg. syncope) - Backward or congestive failure
- adequate output at abnormal pressures - Forward and backward failure
- inadequate output at abnormal pressures (bad)
5 reasons for heart failure?
- Pump failure
- Volume overload
- Pressure overload
- Arrhythmias
- Diastolic heart failure
Is it easy to ID the cause of heart failure?
- no
- final common pathway irrespective of cause (mostly)
What is the final pathophysiology leading to heart failuer?
- real or perceived underfilling of the arterial circulation
initiates a cascade of events leading to heart failure
What diseases cause 1* failure of myocardial systole?
- dilated cardiomyopathy
- coronary vascular disease (inadequate blood supply to area of the myocardium eg. infarct)
Which diseases cause heart failure by volume overload?
- valvular insufficiencies (mitral, arotic)
- shunting diseases (ventricular septal defect, patent ductus arteriosus)
- chronic anaemia
> all cause the cardiac chamber to chronically increase output -> overwork and eventually heart failure
What is the total stroke volume made up of in mitral valve insufficiency?
Forward stroke volume + regurgitant stroke volume
- forward stroke volume is regulated to maintain arterial filling
- sometimes regurgitant stroke volume is = or ^ than forward stroke volume
What is the comonest heart disease of dogs?
Acquired mitral valve regurgitation/insufficiency
Which diseases cause failure by pressure overload?
- Hypertension - systemic or pulmonary
- Narrowing of the outflow tract - aortic or pulmonic stenosis
Which species gets hypertensive disease?
Cats
How may arrythmias cause heart failure?
- low heart rates => v CO
- high heat rates => v SV -> v CO (diastole too short to allow adequate filling)
Which diseases cause failure by diastolic failure?
- Hypertrophic cardiomyopathy
- Dilated cardiomyopathy (myocardial fibrosis) - stiff ventricle difficult to fill
- pericardial effusion
> greater than normal filing pressures needed to maintain CO
> common in cats
Are most causes of heart failure treatable?
No untreatable and irreversible
Average survival for cats with heart failure?
< 1 year
Which systems in the body ^ circulating volume?
- RAAS
- ADH
- Renal autoregulation of flow
WHich systems in the body v circulating volume?
- Natriuretic peptides
- Renal autoregulation of flow
How is the initial response to cardiac disease described? How does this change over time?
- Adaptive
- Maladaptive
- Failure
> due to chronic stimulation which is not normal
What senses a drop in arterial perfusion? What effect does this have?
> CO -> v arterial blood pressure > Baroreceptors - v parasympathetic - ^ sympathetic activity (b) rate and force - (a) blood vessels -> constrction - (b) renin(RAAS) system activated > a and b receptor mediated
What are the effects of barorecepotrs reflex?
\+ chronotrope \+ inotrope \+ luisitrope (relaxation) - vasoconstriction - RAAS
What trend is seen in t heHR in mitral valve insufficiency?
^ HR over time before deat h (chronic symp activation)
Whaen is RAAS activated? What system is acticated next?
Underperfusion of kidneys
- ADH activated next
Which system countacts RAAS and ADH?
Natriuretic peptide system
- if volume too great detected by myocardium
- ^ urine output
How is the netriuretic systme affected by heart disease? -
Volume overload too great
- high cirulating natriuretic levels
- but still not great enough to get rid of excess volume
What does long term RAAS activation cause? How may this be treated clinically?
- excessive fluid retention
- excessive resistance to ventricular emptying
- direct and indirect deleterious effects of myocardium
> antagonise RAAS in canine and human heart failure
Which substances are responsible for local vaso constriction/dilation?
- NO
- PGs
- ENdothelin
What is the final product of RAAS?
Angiotensin 2
What system is activated for profound, severe hypotension? What is this normally responsible for?
ADH
- retention of free water without sodium (i think?? CHECK)
What substances can be used as biomarkers of heart failure?
Natriuretic peptides
- ^ circulating volumes
What ultimately happens to the myocardium with chronic pressure or volume alterations?
> Remodelling or hypertrophy - Adrenergic stimuli - Angiotensin II - Aldosterone - Intracellular calcium > type of loading affects how the heart adapts
What causes concentric and eccentric hypertrophy?
> concentric
- pressure overload (hypertension, aortic stenosis, weights)
eccentric
- volume overload (mitral regurgitation, shunting disease, marathons)
What does chronic hypertrophy cause?
- ^ oxygen demand
- hypoxia
- fibrosis
In what order do the characteristic effects of heart failure occour?
- Short term: alteration in autonomic tone
- Mid-erm: stimulation of endocrine systems
- Long term: Hypertrophy
What are some of the clinical signs of heart failure?
- tachycardia
- poor peripheral perfusion
- fluid retention (RAAS and ADH)
> LCHF: ^ pressure in the left side and pulmonary oedema
> RCHF: ^ filling pressure in right side and oedema from systemic veins (abdo etc.)
What is thromboembolism?
Blood clot breaking off and occluding a vessel
Which diseases causes thromboembolism?
- cardiac disease
- cushing’s disease (hyperadrenocorticism) - parasitic disease
- Protein losign nephropathy
- Neoplasia
- Auto-immune haemolytic anaemia
